Yes most probably 1960s, although your height measurement isn't spot on. It should be either 1 3/16" or 1.5". You need to measure to the nearest 1/16" How strongly the die is stamped in isn't strongly correlated with the era. But yours has the other 3 attributes which are discussed on my site:
http://black.net.nz/avedis/avedis-gallery.html#60s
Brilliant cymbals are documented back into the early 1950s. Sometimes the 1950s ones are called "burnished" rather than brilliant. The tonal grooves aren't worn down as much in "burnishing", although this isn't a distinction metal fabricators would necessarily make. It is something cymbal fanciers have made, and a working hypothesis is that in the 1950s the lathing tools weren't as sharp (or used differently, or something) such that they tended to leave the surface looking "burnished".
The tonal grooves on your example look worn down by the Zildjian "brilliant" process to me. I'm sure I've seen a patent for that but I can't locate it again. If anybody has the patent number that would help.
I haven't finished a web page specifically on the evidence for brilliant cymbals, but I do have a link in my year by year timeline to the first ad for brilliant cymbals being offered which I currently know about. Scroll down in the years and you will see a link to it in 1971. This doesn't mean ads don't go back further in time. I just haven't spotted one yet.
http://black.net.nz/avedis/avedis-by-years.html
Note that if you remeasure and your stamp is indeed 1.25" then I'd love to see a photo of it being measured. There is a 1.25" stamp from the mid 50s at that height which has the 3 dots, but your cymbal doesn't look like one of those because it lacks visible "freestyle" hammering top and bottom. These are mentioned on my site as well:
http://black.net.nz/avedis/avedis-gallery.html#1954
Since that entry was written we* have several landmarks identified on the "1954" stamp which let us tell them from the other stamps (other than by height). If you get a true 1.25" measurement than I'll be surprised, but I'm still surprised on a daily basis. I would then look closer at the landmarks on your stamp pic and see what we can see. I would also ask for a picture of the whole of the underside in "dramatic" side lighting so we might pick up some hammering. Same with the top. But only if you get that 1.25 measurement verified. The top looks machine hammered in the common 1960s style of concentric rings, so there is nothing remarkable on view which would support anything other than 1960s. Same with the bell size and shape, although so far that only provides relatively weak evidence of stamp era (if it were the only thing to go on) except perhaps for the Large Stamps (which that isn't).
* note: The "we" for the 1954 landmarks includes me, Mike Layton, and Adam/CaptainCrunch. Thanks guys.
Bop iT / Til U Drop iT.